A microtome is a device used to cut extremely thin slices, known as sections in the field, from a bulk sample called sample block. To better understand their structural details, these sections are typically subject to inspection and examination under various light microscopes (LMS) and electron microscopes (EMs). A conventional microtome can produce sections having thicknesses in the order of one micron. In contrast, an ultramicrotome can produce sections as thin as 5 nm.
Since thin sections may be delicate, fragile, difficult to extend fully (e.g. twist, fold, and roll up), and sticky to the cutting blade, it is very difficult for a microtome user to handle the sections, for example, to remove them from the cutting blade, and to transfer them to a grid or mesh for further study. To solve this problem, sections have conventionally been collected by floating them on a suitable liquid such as water, alcohol, acetone, and dimethyl sulfoxide. Usually, the side of the cutting blade from which the sections will be dislodged is surrounded by a small trough or boat filled with a liquid having a density greater than the sections. As sections are cut from a sample block, they float on the liquid as a result of buoyancy or surface tension. For example, U.S. Pat. No. 3,225,639 to Martinelli discloses such a design as illustrated in FIG. 1. With reference to FIG. 1, a glass knife 3 having a cutting edge is positioned within a microtome (not shown). The cutting edge is formed by taking an oblong plate of black Cararra glass and fracturing the plate along edge 8 to form the cutting edge. The glass knife 3 has affixed thereto a boat which is represented by the wall 1 of the boat in section. A specimen holder 5 in the full line position can stroke downwardly as indicated by arrow A over the knife edge of glass knife 3. As the holder 5 is so moved, a thin section 7 of the sample is being sliced therefrom. Liquid 4 retained between the boat wall 1 and the glass knife 3 presents a liquid surface upon which the already-separated thin sections 2 from the specimen holder 5 float after the sample has been sectioned. The specimen holder 5 can then move horizontally as indicated by arrow B to the position shown in phantom lines at 6. The specimen holder 5 can be repositioned by moving vertically as indicated by arrow C. After the repositioning, the holder 5 may be advanced represented by arrow D to again be in position to cut another section.
There are at least two problems associated with the liquid floating approach as described above. First, some physical, chemical and biological microstructures and properties of the sections may be adversely altered by their interaction with the support fluid, e.g. ion exchange, disintegration, and partial dissolving. Such interaction may complicate the examination and analysis of sample sections. Second, a section may be adhered to the cutting edge or the previous section forming a floating chain, so a microtome operator has to manually remove the section(s) with a fine brush, or directly pick it up onto a grid or mesh suitable for microscope viewing. As such, the user has to continuously operate and monitor the microtome as each section is produced.
Therefore, microtomic processes in the prior art are not only involving undesirable interaction between floating liquid and sample sections, but they are also repetitive, tedious, laborious, difficult to be automated and therefore less productive. Advantageously, the present invention can solve at least one of the above problems by providing a microtomic system and process utilizing electrostatic force to collect and distribute sample sections, and exhibits technical merits such as automatability, improved efficiency and productivity, and sample integration, among others.